Knuckles the Echidna: Successfully complete all Town Stage missions with an "S" rank.

Miles "Tails" Prower: Successfully complete all Town Stage missions.

Rouge the Bat: Successfully complete all GUN Commander missions.

Audio Room music

Successfully complete the indicated episode with a 100% rank to unlock the corresponding theme in the Audio Room:

Elise's Theme: The Last Episode

Shadow's Theme (All Hail Shadow): Shadow's Episode

Silver's Theme (Dreams of An Absolution): Silver's Episode

Sonic's Theme (His World): Sonic's Episode

Very fast Sonic

In Multiplayer mode in any level or match, equip the Red Gem on Sonic, activate it and hold it, then die. While still holding the activation button, wait until you respawn. When you respawn, deactivate the gem. You will now run much faster than normal and the time will automatically be slow.

Longer jumps with Silver

Jump with Silver by pressing X, then press X again while in mid-air. This makes Silver float around. When floating in mid-air, tap X while moving in any direction instead of holding the button down to make Silver jump further.

Defeating big enemies faster

When facing an enemy that requires more than one hit, use your Homing Attack on it then use your Bounce Attack. Note: You must first have the Bounce Bracelet.

Defeating Silver

When you fight Silver with Sonic, first do a slide move into him as he is falling from the sky. Then, collect a ring and run around until you hear "How bout this?", then do a homing attack on him. Run away again until you hear "How bout this?" again. then do a homing attack again. Repeat this until he is defeated.

Defeating Solaris

First, use Silver to weaken him until his first arm guard falls off. Then, switch to Shadow and hit him with the beams until his second arm guard falls off. Next, use Sonic to defeat the rest of his first form. Finally, use all three to survive the blows of lasers, and continuously attack.